Aerodynamics Of Soccer Balls And Volleyballs

Abstract

The purpose of this study was to investigate range, flight time, speed and trajectory of selected official soccer balls and volleyballs in a constant release angle (18 degree) shot by a ball gun with a hydraulic shooting steel leg mechanism in an indoor soccer hall. Five soccer balls (m=0.422 ± 0.010 kg, d=0.108 + 0.002 rn, p=(0.69 + 0.01) x 105 Nm-2) and five volleyballs (m=0.278 ± 0.006 kg, d=0.105 + 0.002 rn, p=(0.69 ±0.01) x 105 Nm-2) were used. Three speeds of the kicking steel leg were applied to the stationary and rotating balls with two constant angular velocities (45.6 and 65.0 radls). All shots of the balls were recorded with two JVC 707 5-VHS camcorders (50 Hz) for kinematic and kinetic motion analysis. An APAS performance analysis system was used for detailed 3D analysis of the release phase of the shot. The range of the ball was measured in x-z coordinates on the Astroturf ground. A Panasonic camcorder with timer was used to measure the flight time of the ball. A 3- way ANOVA was applied in order to study the differences of the balls and their behaviour in the placid air. The release velocities of the stationary soccer balls with three speed categories .were 18.8 + 0.1 ms·1, 23.1 ± 0.1 msand 26.5 ± 0.1 ms-1 and in volleyballs 20.5 ± 0.2 ms-I, 25.6 ± 0.2 ms-1 and 29.4 ± 0.2 ms-1, respectively. The range of the fastest shot off the soccer balls was on average 44.8 m with the lateral deviation of 3.3 degrees. The average range of the volleyballs in the fastest shots without spin was 45.2 m with the lateral deviation of 4.8 degrees. The average ground speeds in the fastest shots of the soccer ball and volleyball were 20.6 ms-1 and 24.7 ms-1, respectively. With the fastest spin and shot the range and deviation of soccer balls and volleyballs were 34.4 m and 38.6 m and 19.7 and 21.4 degrees, respectively. The main effects of the ball type, shot speed and spin were significant (p<.OOl) on the range, ground speed and lateral deviation. SeveraI2-, and 3- way interactions were found. The deviation of the landing points in x-z coordinates was significantly (p<.OOl) smaller in both ball types with the highest angular velocity than with stationary balls. The results indicated that in the stationary balls with each speed the average range was longer and the deviation in x-z coordinates larger in the volleyballs than in soccer balls mainly due to the lower mass of the volleyball. The "kite" phenomena was observed both in soccer balls and volleyballs. The higher the angular speed of the ball was the shorter the range and the smaller the landing area of the balls were with the corresponding shot speed. More attention should be paid for the detailed analysis of the reasons of the variations. It can be concluded that the trajectories of the balls were in each ball type so constant that ball gun can be used in the training and evaluation of individual techniques of the goalkeepers and field players in soccer. In volleyball all type of serves with spin and "kite" balls are also possible.